Obama has 'no strategy yet' against IS militants in Syria

US President Barack Obama said Thursday that he did not yet have a military strategy for battling Islamic State fighters in Syria as the jihadist group said it had executed scores of Syrian troops, the latest in a string of atrocities.

Dampening hopes of imminent air strikes in Syria, Obama said he was still developing a comprehensive plan to defeat militants from the Islamic State group (IS, also known as ISIL or ISIS), which has also overrun large swathes of Iraq.

"We don't have a strategy yet," Obama said ahead of a meeting with security chiefs.

The admission attracted immediate criticism from Republican lawmakers. White House spokesman Josh Earnest later clarified that Obama was referring to military options, but that a comprehensive strategy for confronting the group through diplomatic means was already in place.

The civil war in Syria has killed some 191,000 people since it erupted in March 2011 with President Bashar al-Assad's bloody effort to put down an uprising. The UN said on Friday that the number of recorded registered refugees had reached a record 3 million.

But the conflict has taken on another dimension as IS jihadists exploited the power vacuum to move in, unleashing a series of atrocities including the brutal execution of US journalist James Foley.

The chaotic situation on the ground was underlined by the seizing of 43 UN peacekeepers on the Golan Heights by rival Islamist rebels, led by al Qaeda affiliate al-Nusra Front.

They were part of a mission that has monitored an armistice between Syrian and Israeli troops on the strategic plateau for decades.

Surveillance flights

Obama's decision to begin US surveillance flights over Syria this week prompted speculation that he was on the brink of expanding the fight against IS from Iraq into Syria and criticism from some lawmakers concerned that they had not been properly consulted over possible US actions.

Obama said he was dispatching Secretary of State John Kerry to the Middle East to build support in the region against the IS jihadists.

The jihadists posted grisly video footage on the Internet of scores of bodies heaped in the desert they boasted were those of Syrian soldiers they captured and killed following the seizure of Tabqa airbase.

They have repeatedly posted gruesome videos, which have appalled international opinion but served as a propaganda tool to recruit volunteers.

Britain-based monitoring group the Syrian Observatory for Human Rights said IS had executed at least 160 soldiers, among some 500 who had made a desperate bid to escape to government-held territory after their defeat last Sunday.

"No need to choose between IS and Assad"

A UN-mandated probe has charged that public executions, amputations, lashings and mock crucifixions have become a regular fixture in jihadist-controlled areas of Syria.

The Syrian government launched air strikes of its own on Thursday, killing six IS leaders, the Observatory said, but Washington has baulked at cooperating with Damascus against the group.

On Thursday, Obama reiterated the stance, saying: "I don't think there's a situation where we have to choose between Assad or the kinds of people who carry on the incredible violence that we've been seeing there."

Washington has also been weighing both aid drops and air strikes in Iraq to help residents of a Shiite Turkmen town besieged by the jihadists since early June, US officials said on Wednesday.

"It could be a humanitarian operation. It could be a military operation. It could be both," said a US defence official on condition of anonymity.

UN Iraq envoy Nickolay Mladenov has called for an urgent effort to help Amerli, saying residents face a "possible massacre" if the town is overrun.

The Washington Post reported Thursday that at least four Western hostages held by the Islamic State in Syria, including the murdered Foley, were waterboarded in the early part of their captivity.

Waterboarding, which was used by the CIA during interrogations of suspected terrorists after the September 11, 2001 attacks, is a widely condemned form of torture that simulates drowning.